What's interesting is that the loss of ice could actually lead to feedback effects which could make it easier for ice to form. Quite what will happen as a result of all these competing effects is still anybody's guess.

The ice loss is most pronounced in the deep waters near the centres of the lakes, as here heat stored heat in the summer slows down the formation of ice. Shallow waters near the coasts are not losing as much of their ice.

As with sea ice, removing the ice cover means that more sunlight can penetrate the lake, heating it up more and making it even less likely than ice will form: a positive feedback loop.

However, the extra heat also causes more evaporation, leading to lower water levels. These shallower waters would release heat faster - and therefore be more likely to ice over in winter.

Lead researcher Jia Wang says it's unclear which of these effects will win out.

Whatever happens, it's likely to matter. Less ice on the Great Lakes would be a boon for shipping and pleasure boats - but less water in them would be anything but.

In other words, no global warming and ice patterns are no different from the normal mean and variation.

I come from that part of the country and a couple of things should be noted: Lake Michigan rarely freezes over; this happens only a few times every century. Second, there is no natural water level of the great lakes. The level has gone way up and down ever since explorers and settlers began observing the lakes. And third, most rainfall (and snowfall) that's fed by evaporation from the lakes falls right back in its own watershed.

Mandy
on March 24, 2009 8:23 PM

True the lake rarely freezes over but the areas of ice coverage as shown by the graph in the link is definately trending downwards.

I presume the amount of water entering the lakes in the winter is redued as the precipitation falls as snow rather than rain and has to wait for a thaw before it becomes run off to go back into the lakes.

Trey
on March 25, 2009 1:41 PM

*Quite what will happen as a result of all these competing effects is still anybody's guess* Regardless of this scientific conclusion I think we should still freak out about it and spend trillions of dollars to prevent whatever it is that’s going to happen.

Nothing I can think of can be more vital to a good enough future for the children than a global flow of ideas regarding the population dynamics of the human species on Earth. A virtual mountain of scientific knowledge supports the near-universal understanding that a finite planet with the size, composition and frangible ecology of Earth cannot be expected to much longer support an endlessly growing number of human beings worldwide, many too many of whom appear to be willfully choosing to increase in an unbridled way their conspicuous per-capita consumption and unnecessary overproduction of stuff.

With the hope of promoting necessary discussion of the subject of global human population growth, I would like to share a recent email from one of our most respected colleagues, Dr. Gary Peters, a splendid contributor to the blogosphere.

begin----

"Steve has mentioned the work below but I'm not sure how many of you have actually been able to look at it. It is solid and worth your time, especially if you have an interest in population growth and any variation on the idea of sustainability.

Gary

www.panearth.org

P.S. For those who like such data, the world population now grows by close to 220,000 people per day."

end ---

If you will, please rigorously examine the presentation, World Food and Human Population Growth.

Usual objections to the research of Russell Hopfenberg, Ph.D. and David Pimentel, Ph.D., have focused the human community's attention upon "Demographic Transition Theory." Although this theory is descriptive in character, the demographic transition theory has been widely shared, consensually validated and erroneously deployed, by many too many demographers and economists in particular, as a tool for effectively predicting the end of population growth soon and the automatic stabilization of the human population on Earth in the middle of Century XXI.

With remarkable clarity the research of human population dynamics by Hopfenberg and Pimentel shows us that, as a predictor of the increase or decrease of absolute global human population numbers, the theory of the demographic transition is fatally flawed and directly contradicted by more adequate scientific evidence.

While the theory of the demographic transition does offer a useful historical view of recent patterns of human population growth, its value as a tool to forecast the increase or decrease the population numbers of the human species worldwide can now be seen, in the light of new research, as fundamentally defective.

If the human family continues choosing to keep doing precisely what we are doing now as absolute global human population numbers skyrocket toward a projected 9+ billion people, can reason or common sense possibly support the idea that future outcomes regarding human population growth will be any different either from the results we are seeing now or the results which have been occurring throughout recorded history?

Perhaps someone will kindly explain what you think will happen that would effectively lead to the stabilization of population numbers of the human species in the year 2050, given the fully anticipated young age distribution of the global human population at that time?

At the midpoint of the twenty-first century, what do you suppose hundreds upon hundreds of millions of fertile young people, who are expected to be capable of reproducing, will be doing with their sexual drives and instincts other than what their ancestors did for thousands of years?

Psychologists have often commented about such circumstances in this manner: doing the same things over and over again while fully expecting that a new succession of events will somehow magically occur is an example of extreme foolishness.